Direct access storage devices (DASDs) have become part of everyday life, and as such, the capability to manipulate and store larger amounts of data at greater speeds is expected. To meet these expectations, DASDs such as a hard disk drive (HDD) have undergone many changes.
The basic hard disk drive model resembles a phonograph. That is, the hard disk drive model includes a storage disk, or hard disk, that spins at a standard rotational speed. An actuator arm with a suspended slider is utilized to reach out over the disk. The arm carries a head assembly that has a magnetic read/write transducer, or head, for writing or reading information to or from a location on the disk. An air bearing surface (ABS) on the slider allows the slider to be flown very close to the surface of a disk. The complete head assembly, e.g., the suspension and head, is called a head gimbal assembly (HGA).
Data is recorded onto the surface of a disk in a pattern of concentric rings known as data tracks. One way to increase the amount of data that can be stored on a disk is to make each data track narrower so that the tracks can be placed closer together. But, as tracks are narrowed, the signal-to-noise ratio is worsened, making it more difficult to discern signals from the head. Signal-to-noise ratio can be improved by positioning the head closer to the disk surface. Thus, the height of the slider above the disk (referred to as fly height) can be an important parameter. Another important parameter is the distance between the bottom surface of the head and the bottom surface of the substrate to which the head is attached (referred to as pole tip recession). In general, as the spacing between the head and the disk surface is narrowed, it becomes more important to tightly control the flatness and uniformity of surfaces such as the ABS, in order to reduce the probability of contact between the head and a disk.
When forming the ABS on a slider, a planarization surface is needed. That is, the sliders are laid out on wafers and then cut into rows or bars. At the bar level, the ABS is formed on each slider. Since the bars are so small, a number of bars are often placed on an adhesive material and the spaces between the bars are filled with a flowable material to form a planarized surface upon which to work. However, with distances and tolerances measured in terms of nanometers, even minute deviations in the topography of the planarized surface can be very significant. For example, the utilization of some flowable materials will result in corners of the planarized surface pulling away from the bars during the cure process, or it may be extremely difficult to remove the flowable materials from the bars when the forming of the ABS is complete. Thus, there may be a great loss of yield based on curing, removal, and the like.